It would be naive to suggest that those figures you've linked actually reflect reality. One needs to consider the social stigma still unfortunately associated with homosexuality.
We know that a huge percentage of homosexual men and women remain in the closet and thus would not identify themselves as homosexual, or admit to having any homosexual contact.
The report you link mentions this on page 127:
WE have suggested that sexual expression may be characterised more as a spectrum than a
dichotomy and that individual identity, attraction and experience may be combined in complex
patterns. The relationship between sexual attraction and experience is important. Though the level of
stigma associated with homosexuality has decreased in recent decades, it is still pronounced in Irish
society. This means that all estimates of same-sex attraction, experience and identity based upon selfreports should be seen as under-estimates.
However, if sexual attraction can be seen as an indicator of an inclination toward same-sex
relationships, we would expect that, given the level of stigma still associated with homosexual
behaviour, the level of same-sex experience reported would be lower than the proportion reporting
same-sex attraction. By the same logic, we would expect that the prevalence of current homosexual
partnerships would be far lower than the proportion that have ever had genital contact with the same
gender or homosexual intercourse (ie, anal or oral sex).
The small proportion defining themselves as anything other than heterosexual means we should be
careful in interpreting these statistics. The small numbers involved (1% of the sample defining
themselves as homosexual would total just 57 individuals) mean that the standard errors and
associated confidence intervals are large. We have no comparable figures for the NATSAL surveys in
Britain, but figures from the Australian ASHR survey 6 and US NHSLS 5 are very similar. The figures
suggest that very few Irish people could be said to be ‘homosexual’, but, as already argued, sexual
identity is not necessarily aligned with either sexual attraction or sexual experience.
Also interestingly on page 131 of the report there's a table of the percentage of self-identified homosexual (and those who admitted homosexual contact) with respect to age groups. It is clear that the amount of self-identified homosexuals decreases with increasing age.